The present disclosure generally relates to filter elements utilizing shaped particle-containing non-woven webs. More particularly, the present disclosure relates to filter elements including shape-retaining self-supporting non-woven webs, wherein the web possesses a three-dimensional deformation. The present disclosure is also directed to respiratory protection systems including such filter elements.
Respiratory protection devices for use in the presence of vapors and other hazardous airborne substances often employ a filtration element containing sorbent particles. Design of such filtration elements may involve a balance of sometimes competing factors such as pressure drop, surge resistance, overall service life, weight, thickness, overall size, resistance to potentially damaging forces such as vibration or abrasion, and sample-to-sample variability. Fibrous webs loaded with sorbent particles often have low pressure drop and other advantages.
Fibrous webs loaded with sorbent particles have been incorporated into cup-like molded respirators. See, e.g., U.S. Pat. No. 3,971,373 to Braun. A typical construction of such a respiratory protection device includes one or more particle-containing and particle-retaining layers placed between a pair of shape retaining layers. See, e.g., U.S. Pat. No. 6,102,039 to Springett et al. The shape-retaining layers provide structural integrity to the otherwise relatively soft intermediate layer, so that the assembly as a whole would retain the cup-like shape.
There remains a need for filtration elements that possess advantageous performance characteristics, structural integrity, simple construction and are easier to manufacture.